The invention relates to an analog-to-digital converter incorporating a series arrangement between an input and an output terminal of the converter, comprising an integrating circuit, a comparison circuit, a flip-flop and a coincidence gate, a clock pulse input of the flip-flop and an input of the coincidence gate being connected to a clock pulse input terminal of the converter, the converter incorporating, provided in a feedback path, a switchable current source circuit, a current source output terminal of which is connected to an input of the integrating circuit and which is further coupled to the input terminal of the converter, and a current source change-over terminal which is connected to a flip-flop output.
Such an analog-to-digital converter is disclosed in U.S. Pat. No. 4,112,428 in which it is stated that the described structure of the converter incorporating the switchable current source circuit results in a linear conversion of the analog input signal into a pulse train of the clock pulses. The current source circuit comprises a current source which is incorporated in a bridge circuit formed by switches which are controlled by output signals of the flip-flop. The construction of the integrated circuit is not further described and it is only stated that an optimum integration is effected. A linear conversion is only obtained when such an assumption is accepted.